The present invention relates to a method for processing of calls terminating in a packet switched protocol based communication network that comprises a packet switched based cellular telephone network, for instance, an Internet Protocol based GSM (Global System of Mobile communication) network, and a further network, for instance, an internet protocol network or a general switched telephone network (GSTN) that is coupled to the cellular telephone network by means of an interface comprising a signalling information exchange function and a call or payload information exchange function between the cellular telephone network and the GSTN.
Recently, there have been made attempts in a more and more increasing manner to couple and to integrate a mobile cellular telephone network, for instance, the GSM network that is generally a circuit switched network to a further kind of networks, called packet switched networks, for instance, an internet protocol network or VOIP (Voice on Internet Protocol) network, wherein call information is transferred in the form of xe2x80x9cpacketsxe2x80x9d between the called member and the calling member and vice versa. The packet switched network uses several different ways or through-connections to transfer the packets between the users, whereas in the circuit switched world, for instance, the GSM network, a through-connection is established within the network and, as long as the through-connection is maintained, the whole call information including signalling and payload information is transferred via the through-connection in the circuit switched network between the users.
A through-connection in a communication network that comprises, for instance, a GSM network or a similar cellular telephone network and an internet protocol network or packet switched network being coupled with each other by interface means is established in the conventional cellular telephone network via a base transceiver station, a base station controller and a mobile services switching centre to the interface that in turn is coupled to the internet protocol network or packet switched network. Each node in a packet switched network which processes the payload information causes some delay in the payload transport. This renders the known architecture of the GSM telephone network improper or not very well suited for coupling and integration to a packet switched network, for instance, an internet protocol network or similar network.
Thus it is an object of the present invention to provide a communication network that has a packet switched protocol cellular telephone network architecture and a method for processing information flow of calls terminating in this communication network which minimise the delay problems and bandwidth requirements.
Accordingly, the communication network of the invention has a packet switched protocol based cellular telephone network comprising a first layer for transferring signalling information assigned to a telephone call being processed by the communication network, a second layer for transferring payload information assigned to the telephone call and interface means for coupling the cellular telephone network to a further network, e.g. a general switched telephone network (GSTN), the interface means comprising signalling information exchange function between the cellular telephone network and the further network and payload information exchange function between the cellular telephone network and the further network, the first layer and the second layer of the cellular telephone network being coupled to the interface means, wherein the second layer of the cellular telephone network transfers the payload information of the telephone call to and from the interface means on a direct route assigned to the telephone call within the second layer and the first layer of the cellular telephone network comprises controlling means, e.g. a gateway mobile services switching center, for controlling the routing of the telephone call initiated from the further network and terminating in the packet switched protocol based cellular telephone network.
Since in the invention the payload of a call is routed directly within the second layer of the cellular telephone network to or from the interface means the payload information is not transferred via the longer and more time consuming way of the conventional systems, i.e., for instance, the mobile services"" switching center of a conventional GSM network, and, therefore, a corresponding delay in the cellular telephone network and the delay and bandwidth problems involved therewith are minimised or they are avoided in the communication network of the invention.
The interface means can comprise media gateway means for payload information exchange between the cellular telephone network and the further network and the mobile services switching center can be connected to the media gateway means to control the media gateway means. By selecting the mobile service switching center as media gateway controller, a large part of the conventional GSM functionality can be reused in the communication network of the invention and the media gateway functionality can be kept simple in the communication network of the invention.
The inventive method for processing a telephone call in a packet switched protocol based communication network comprising a further network, e.g. a general switched telephone network (GSTN), and a packet switched protocol based cellular telephone network having a first layer for transferring signalling information assigned to the telephone call being processed by the communication network, a second layer for transferring payload information assigned to the telephone call, and interface means for coupling the cellular telephone network to the further network, the interface means comprising a signalling information exchange function and a payload information exchange function between the cellular telephone network and the GSTN network, the first layer and the second layer of the cellular telephone network being coupled to the interface means, wherein the method of the invention comprises:
initiating a call by the further network, forwarding an initial address message assigned to the call from the further network to the cellular telephone network;
after receiving the initial address message, providing routing information by the cellular telephone network on the basis of the initial address message in order to route the call to a terminating mobile station of the cellular telephone network and
establishing a through-connection for transferring payload information assigned to the call within the packet switched protocol based cellular telephone network from the terminating mobile station via the second layer and the interface means to the further network and/or vice versa.